Computer readable memory is in wide and varying use among portable devices such as for example mobile terminals, navigation systems, portable media players, and smartphones which incorporate many of those functions into a single handheld device. One memory technology utilized by many specific implementations of these portable devices is a memory card such as a removable memory module card MMC and/or an embedded memory module card eMMC, which is a trademark of the MultiMediaCard Association (MMCA). As used herein, removable memory card or module means removable from a host device by an end user without dis-assembling the host device. Memory module cards, whether removable or embedded, are referred to herein as MMCs. Operation of MMCs is largely but not entirely directed by published standards such as the MMC System Specification v4.1 and 4.2, such as to meet advertised interface speeds of 52 MB/sec at an interface voltage of 1.8v or 3.3v.
A problem exists in such MMC devices in that the continuous electrical power supply from the host portable device into which they are integrated might be interrupted, such as for example if the device were physically dropped and the battery dislodged due to the impact. This has led to strict requirements for the MMC device itself so as to withstand data corruption despite a sudden loss of electrical power. Meeting these requirements has resulted in the performance of the MMC component being degraded somewhat; there is an engineering tradeoff between memory speed and data reliability in this instance where power supply might be interrupted. This is because the internal operations of the MMC are limited so as to assure the required data reliability under the above conditions of power loss.
Current solutions to assure the above data reliability for mobile device mass memory consider that power supply can be lost at any moment, as in the above dislodged battery scenario. In many implementations this means that data storage and buffering inside the MMC component itself is implemented using non-volatile memory technology (by example, NAND logic in at least eMMCs). A performance degradation arises because non-volatile memory technology typically has much lower performance (by example, write speeds for data) than volatile memories such as dynamic random access DRAM memory technologies.
There are some prior approaches to address the problem of data loss from a dislodged battery. US Patent Publication 2010/0122023 describes that if it is determined that a device is in a free fall situation data is transferred from the random access memory RAM using a non-volatile RAM, similar to that noted above. US Patent Publication 2007/020528 describes that a memory write from a first memory for non-critical data to a second memory for critical data is prevented if the host device is in free fall. US Patent Publication 2005/0279165 describes that a data transfer stop instruction is issued if it is determined that the device is in free fall.
Embodiments of the invention detailed below are directed to improving performance/speed of the MMC, and as such may be utilized in conjunction with the above solutions for preventing data loss in the event of complete power interruption. The below embodiments are exemplary and non-limiting, and the broader teachings herein are not limited only to specifically MMC memory but to any type of mass memory implemented in a device which has different modes of performance and which is subject to interruption of continuous electrical power.